The present invention pertains to plumbing apparatus and more particularly pertains to a plumbing assembly for use in conjunction with a hydronic heating system.
Hydronic heating systems use water (or water-based solutions) to move thermal energy from where it is produced to where it is needed. The overall hydronic system consists of four interrelated parts: (1) a heat source; (2) a distribution system, or piping; (3) heat emitters (e.g., baseboard conductors, wall panel radiators, radiant floors); and (4) a control system, or controller. Upon demand for heat, water is circulated around the piping by the distribution system. The distribution system carries heat from the heat source to the heat emitter where it is released into the heated space.
In an ideal application, the rate at which the water absorbs heat from the heat source would exactly match the rate at which the heat is released by the heat emitters. This rate would also, ideally, match the rate of heat loss from the building. Unfortunately, in real applications, such ideal conditions seldom exist. A high performance boiler, for example, can deliver heat to a building much faster than the building loses heat on a mild day. Continuous operation of the boiler under these circumstances would quickly overheat the building. Different types of heat sources, such as boilers, (gas-, oil-fired, electric, condensing versus non-condensing) domestic hot water tanks, heat pumps and solar energy systems, present different control challenges for the system designer.
Irrespective of the type of heat source used, system control falls into one of the following categories: (i) on/off control; (ii) staged control, (iii) modulating control, or (iv) outdoor reset control.
On/off control devices operate by simply opening or closing electrical contacts and are by far the most common type used in hydronic heating systems. Control components such as room thermostats, burner relays and set point controls all function by either allowing or preventing an electrical signal to pass through a set of contacts. When on/off control devices are used to regulate the heat output of a system, they can only do so by turning the heat source on and off. They cannot vary the rate of heat output of the device they control. For example, turning a room thermostat to a high setting does not make the boiler burn fuel at a faster rate. It only keeps it on for a longer time while the room temperature increases toward the higher set point.
This presents a problem in heating systems having low thermal mass. On/off cycling tends to make the room stuffy or make people feel drowsy. When the furnace is shut off, drafts from windows and doors quickly re-establish themselves, which decreases comfort.
Staged control, however, increases the heat capacity of the heat source in fixed increments as the load increases. The number of increments, or stages, between zero and maximum heat output can vary from two to twelve or more. The higher number of stages is more common in larger commercial systems. The practicality of using a multi-stage heat source depends on the total heating load of the building and the type of heat source used. Two-stage operations can be considered for gas boilers or hydronic heat pumps. In such cases, a modular boiler (or modular heat pump) system using two identical units may be used. Electric boilers come with staged heating elements. Larger residential and light commercial buildings are very adaptable to multi-stage controls. In making the decision, the designer must weigh the extra cost associated with a multi-stage system against the potential fuel savings and more accurate system control.
Another type of control system, modulating controls, allow continuous variations in heat output over a range from zero to full output. Modulating controls are based on controlling the temperature of the water supplied to the heat emitters. As the supply temperature decreases, so does heat output. One method of doing this uses a motorized mixing valve to create a specific outlet temperature based on the proportions of supply and return water entering it. Another way is the use of a variable speed pump to inject hot water in a constantly circulating distribution circuit. Still another method, used with electric resistance boilers, is to control the electrical current through the element(s) using solid state power regulating devices. Additionally, some non-electric hydronic system components, e.g., the thermostatic radiator valve, also operate as modulating devices. Motorized mixing valves, variable speed pumps and regulating devices add significantly to overall cost and the number of man hours for system installation.
The fourth type, and perhaps the best method for matching the heat output of a hydronic system to the heating load of a building at any given time is the outdoor reset control. This control method makes small but frequent adjustments to the water temperature supplied to the distribution system. Sensors monitor the outdoor temperature and the temperature of the system. As the outdoor temperature decreases and building heating load increases, the supply water temperature is raised. When outdoor temperature increases, the supply water temperature is decreased. This is accomplished by increasing the rate at which heated water is injected into the distribution system. A variable speed controller and pump are typically used.
On/off control, staged control, modulating control and outdoor reset control describe the type of output signal(s) from the controller. Several control components are necessary to build an overall control system, and the components respond to the signals in different ways. For example, a pump may start, stop or run at a certain speed, while a mixing valve actuator may rotate very slightly. Control components add significantly to the overall cost of the system. They add installation procedures and man hours and must be carefully adjusted as determined by the type of heat source as well.
Additionally, combining control components is not simply a matter of choosing a favorite pump and valve and connecting them. Major subsystems such as the heat emitters and the heat source have certain temperature and flow rate changes that have to be observed if they are to function properly and meet their lifetime expectancy. Retrofit systems present special challenges if the subsystems are to remain intact. Failure to respect the operating characteristics of these subsystems and control components will result in installations that either underheat, overheat, waste energy, (e.g., cause corrosion of cast iron and steel in those types of boilers) or otherwise disappoint building occupants.
Thus, the goal of the designer of a hydronic heating system is to ensure that thermal equilibrium is established at conditions that properly heat spaces, but do not adversely affect the operation or longevity of the system""s components.
Therefore, it is highly desirable to provide a new plumbing assembly for use in conjunction with a hydronic heating system.
It is also highly desirable to provide a new plumbing assembly that is removably connectable as a single unit to the distribution system and heat source.
It is also highly desirable to provide a new plumbing assembly that is capable of minimizing a hydronic heating system""s use of expensive mixing valves, variable speed controllers or power regulating devices regardless of the control method under which such a heating system operates.
It is also highly desirable to provide a new plumbing assembly that is inexpensive to manufacture, easy to install and accommodates retrofit applications.
It is also highly desirable to provide a new plumbing assembly capable of controlling the heat output of a hydronic heating system so that it closely matches the current heating load of a building irrespective of the type of heat source used. Such plumbing assembly also must accommodate the on/off control, staged control, modulating control or the outdoor reset control method, respectively, or in combination.
It is also highly desirable to provide a new plumbing assembly capable of accommodating variable temperature and flow rate changes characteristic of major subsystems.
It is finally highly desirable to provide a new plumbing assembly that meets all of the above desired features.
Therefore, it is an object of the invention to provide a new plumbing assembly for use in conjunction with a hydronic heating system.
It is also an object of the invention to provide a new plumbing assembly that is removably connectable as a single unit to the distribution system and heat source.
It is another object of the invention to provide a new plumbing assembly that is capable of minimizing a hydronic heating system""s use of expensive mixing valves, variable speed controllers or power regulating devices regardless of the control method under which such a heating system operates.
It is yet another object of the invention to provide a new plumbing assembly that is inexpensive to manufacture, easy to install and accommodates retrofit applications.
It is another object of the invention to provide a new plumbing assembly capable of controlling the heat output of a hydronic heating system so that it closely matches the current heating load of a building irrespective of the type of heat source used. It is also an object of the invention to accommodate the on/off control, staged control, modulating control or the outdoor reset control method, respectively, or in combination.
It is still another object of the invention to provide a new plumbing assembly capable of accommodating variable temperature and flow rate changes characteristic of major subsystems.
It is finally an object of the invention to provide a new plumbing assembly that meets all of the above desired features.
In the broader aspects of the invention, there is provided a plumbing assembly for maintaining the temperature equilibrium of a hydronic heating system that has a heat source for heating fluid and a distributing means for distributing the heated fluid to at least one radiant zone and returning the fluid to the heat source. The plumbing assembly comprises a zone supply conduit with a supply port and a zone return conduit with a return port. A heat loop comprising a first conduit with a supply end and a return end is included. A bypass valve is connected to the first conduit between the supply end and the return end for controlling the flow of fluid from the supply end through the first conduit to the return end. A first looped conduit is connected to the first conduit upstream from the bypass valve, and a second looped conduit is connected to the first conduit downstream from the bypass valve.